It happened on a December morning a long 12 years ago, but Zinab Aribi can still describe it in precise detail. She remembers how she heard the trucks outside, saw the uniforms of the gendarmes and respectfully let them in when they knocked at the door of her apartment in a poor district of eastern Algiers.

She tells how they asked for her eldest child and then led away Hocine, who was just 18. She recalls their exact words when they said to him, "We need you just for a few minutes", and how, when he never returned, she spent years looking for him in vain at police stations, prisons and morgues. Finally, she describes how she still prays to be delivered of her guilt and grief and to have the front door open once more and Hocine walk back in.

Algerians say it was a dirty war, and it was. At least 150,000 people died, often civilians and often victims of terrible brutality. A civil war broke out in 1992 after the government cancelled parliamentary elections when it became clear a popular Islamist party would win. The authorities responded to attacks by guerrillas with ferocious repression. As well as the dead, there are perhaps 10,000 like Hocine, "les disparus", seized from their homes by the security services and most likely killed and buried in still-secret mass graves. Several hundred also disappeared at the hands of Islamist groups.

Today, Algerians vote in a referendum on a new charter for "peace and national reconciliation", essentially a sweeping amnesty that will forgive guerrillas who lay down their arms and, by implication, the police officers and security agents who also committed terrible crimes. It recognises for the first time the cases of the disappeared and promises to compensate their relatives.

Yet there is much that the charter does not say. What Algerians like Mrs Aribi want is the truth about what happened in those years of war - and that is not on offer.

"We don't know where Hocine is," says Mrs Aribi, 58, sitting in her apartment beneath a portrait of her missing son. "Is he alive or dead? Did they bury him? Was he killed by wild animals? Is he in prison but psychologically damaged? We don't know." She says the truth is now more important to her than getting revenge against the men who took him.

"Why let us suffer? If a man comes in the middle of the night and tells me he buried my son, I will forgive him. We just want the truth. It is not me that will make them pay, it is God," she said.

In the first few years, she received news from former prisoners who described seeing Hocine in the infamous Chateau Neuf secret detention centre in Algiers. But those reports dried up and, since then, there has been no word.

Her friends tell her her son must be dead; she tells her five other children he will come home. "If we vote yes in this referendum, it is for our young people so they can live in peace," she says. "We have no other country. We must live with each other."

There is little doubt the charter will be approved, because debate has been tightly controlled. But many are concerned it will simply enable the state to draw a line under the crimes of the past.

"I hope the referendum will not be the end but rather the beginning of a process," says Safia Fahassi, who heads the National Coordination for the Families of the Disappeared. Her husband, Djamil, a journalist, was taken by the security services 10 years ago. "I hope it will encourage these people to feel more at ease to talk about what happened so these things will not be repeated in the future."

International rights groups are critical of the charter. Human Rights Watch says it will reinforce the "impunity" of the police and security agents who committed atrocities. Amnesty International says it is concerned it may be a "final denial of truth and justice to hundreds of thousands of victims and their families".

The charter talks boldly of a new future for Algeria, but praises the army and the security services, who played a major role as perpetrators in the war, and explicitly absolves the state of responsibility for any crimes. In its most telling sentence it states: "The sovereign Algerian people reject all allegations intended to hold the state responsible for a policy of disappearances."

It offers no promise of investigations into the killings and tortures of the past nor sets up any form of truth and reconciliation commission.

There are also vaguely worded warnings that no one should "use or instrumentalise the wounds of the national tragedy to harm the institutions of the People's Democratic Republic of Algeria", which may prevent people bringing cases against the government for rights abuses committed during the war.

The charter is at the heart of the political programme of the president, Abdelaziz Bouteflika. He came to power in 1999 and has won two elections. Some analysts suspect he is using the "national reconciliation" policy to win a third term in office.

There is little doubt that political violence has abated since Mr Bouteflika came to power, though there have been a series of deadly attacks against soldiers in the past week in the countryside - a sign that the war is not yet over.

In recent days, Mr Bouteflika has toured the country campaigning on the referendum. At an indoor stadium in Algiers on Monday, where he was protected by hundreds of armed police, he tried to play the democrat, telling the crowd: "You are free to choose yes or no."

Posters of the president were pasted around the stadium walls and a balloon display hung from the roof in the national colours of red, white and green spelling out the words, "Yes for peace and reconciliation".

And he made it clear that the Islamic Salvation Front, the party which was set to win the vote in 1992, would not be allowed back into politics. "I tell you that the people who were responsible for setting fire to this country are not allowed to come again on to the political scene," he said.

Some within the establishment say this hardline approach means few Algerians now have confidence in the government. The tensions of the war are now exacerbated by dire poverty and serious unemployment.

"You cannot deny political Islam exists or eliminate it by using force," said Abdulhamid Mehri, a former head of the ruling party, the National Liberation Front, and a former government minister.

"This charter tries to bring solutions to the effects of the crisis but it doesn't solve the crisis itself. We are continuing the same policy that was started in 1992. It was the absence of democracy that created all the extremism."

History: after the colony

1962 Algeria wins independence from France, its colonial master since 1830, after eight years of conflict in which a million Algerians lost their lives. Ahmed Ben Bella elected president the following year

1965 Ben Bella overthrown by Colonel Houari Boumedienne and spends 15 years under house arrest

1976 New constitution introduced and Islam recognised as state religion

1992 Recently formed Islamic Salvation Front (FIS) wins first round of general election. Assembly is dissolved and the president resigns under military pressure. Mohamed Boudiaf becomes head of the Higher State Council. A crackdown on political activity follows, FIS are banned, Islamic insurgency begins and a state of emergency is declared. Boudiaf is later assassinated